I have tried to export to print-ready PDF a fairly straightforward A4 advet. There's nothing complicated or unusual about the file - its based on ones we've successfully done previously.
However, this one give me a 'FAiled to Export the PDF file' error - but nothing more. I have tried restarting the Mac but to no avail.
What Mac? What PDF settings? What fonts, paragraph styles, linked files, other fancies? You will have to provide a lot more info. in any case, ask in the ID forum...
Moving discussion to Indesign forum.
Save as IDML and export again